Along with the increase in the spread of smartphones, the use of smartphones while walking has increased, and the resulting accidents has also increased. There are signs and exclusive roads implemented to prevent accidents caused by smartphone use while walking, but these measures are limited to specific areas. So, this paper creates a system to assist pedestrians without limitations to specific locations, utilizing the LiDAR sensor of the iOS Pro model. LiDAR provides accurate height information for objects in the frontal direction compared to a camera. However, the LiDAR detection range for the front varies depending on the angle of the smartphone, and individuals may use the smartphone at different angles. To address this, the angle of the smartphone is measured using an acceleration sensor. But the angle error caused by the change in acceleration during walking. So this error is corrected using the firstorder low-pass filter, and the angle is 4.13% more accurate than before the correction. Three LiDAR ranges are set according to the angle, and the height change is detected using the first-order low-pass filter. Finally, a pedestrian assistance system is created to alert pedestrians to danger if the height is more than 10cm before.